In the field of data communications, it is known to transmit data from a sender to a receiver in the form of data units, where each data unit contains some form of appropriate information that lets forwarding network entities guide or route the data unit to its intended destination, i.e. the receiver. This will briefly be explained with reference to FIG. 1. FIG. 1 shows a communications network 2 and communication devices 10-14, which are capable of accessing network 2. Network 2 is shown as comprising a plurality of forwarding entities 21-25. It is noted that the representation in FIG. 1 is only schematic and that real networks generally comprise a far larger amount of forwarding entities and accessing entities. It is noted that within the context of the present specification and claims, any functional element capable of interacting with or interacting in a communication network will be referred to as a network entity. Moreover, it may be noted that the term entity refers to any element capable of providing a certain function (such functions e.g. being sending and/or forwarding and/or receiving), where an entity can be provided by hardware, software or any suitable combination of hardware and software, and an entity can be provided by one physical unit (such as a computer, server, telephone terminal, etc.) or can be spread over several physical units.
In the schematic example of FIG. 1, if e.g. network entity 10 sends data to network entity 11, it will divide the data to be sent into segments, place the segments into data units, where each data unit has a structure defined by the communication protocol governing the communication over network 2. A communication protocol is a set of rules for arranging data and for handling data in entities operating in accordance with the protocol. Examples of such communication protocols are TCP (Transmission Control Protocol), XCP (eXplicit Control Protocol) or various versions of ATM (Asynchronous Transmission Mode) protocols.
FIG. 3 shows a schematic example of a data unit 21. In this example, the data unit has a beginning identifier 31, an ending identifier 32, a header 33 and a payload section 34. The data segment to be sent to the receiver is placed in the payload section 34, whereas information related to the forwarding and handling of data unit 21 is set in the header 33 in accordance with the rules laid out by the protocol governing the transmission. For example, the protocol can prescribe that a specific field 331 is a forwarding data field containing information that is used by forwarding network entities for forwarding the data unit 21 to the designated receiving network entity. Such information can e.g. be an address within an addressing scheme provided by the protocol. It is noted that the term field within the present specification and claims relates to any identifiable section of a data unit, where such a section may consist of a contiguous number of data symbols (e.g. bits), or can be spread out over the data unit. Furthermore, it is noted that various protocols use different names for their basic data units, such as protocol data unit, frame, packet, etc., and that the term data unit is used generically in the present specification and claims to relate to any such subdivision of data being sent in accordance with a given protocol.
Consequently, if sending network entity 10 would like to transmit data to receiving network entity 11, it divides the data into segments and places these segments into data units 21, in which appropriate information leading towards network entity 11 is set in field 331. These data units 21 are then passed into the network, e.g. forwarding network entity 21 as shown in FIG. 1. Forwarding network entity 21 then handles and forwards the data units in accordance with the rules given by the underlying protocol, such that these data units pass to receiving network entity 11 via further forwarding entities 22, 23, 24 or 25, 24. This concept is well known in the art and therefore does not need to be described in further detail here.